Chemistry 0620 · IGCSE · Preparation of salts

Preparation of salts — practice question

Copper(II) sulfate crystals, $\text{CuSO}_4\cdot5\text{H}_2\text{O}$, are hydrated. Copper(II) sulfate crystals are produced when copper(II) carbonate reacts with dilute sulfuric acid. The overall equation is given below. $\text{CuCO}_3 + \text{H}_2\text{SO}_4 + 4\text{H}_2\text{O} \rightarrow \text{CuSO}_4\cdot5\text{H}_2\text{O} + \text{CO}_2$ step 1 Powdered solid copper(II) carbonate is put into 50.0 cm$^3$ of 0.05 mol/dm$^3$ sulfuric acid until copper(II) carbonate is left in excess. step 2 The surplus copper(II) carbonate is removed from the aqueous copper(II) sulfate. step 3 The aqueous copper(II) sulfate is heated until the solution becomes saturated. step 4 The solution is left to cool so that crystals form. step 5 The crystals are taken out and dried.
(a)[3]

Calculate the greatest mass of the copper(II) sulfate crystals, $\text{CuSO}_4\cdot5\text{H}_2\text{O}$, that can be formed by following these steps.

(b)[1]

Explain why this happened.

(c)[2]

State two observations that would show copper(II) carbonate is in excess in step 1.

(d)[2]

Give a reason for this. Explain your answer using particles.

(e)[1]

Name a different substance, other than copper(II) carbonate, that could be mixed with dilute sulfuric acid in step 1 to make copper(II) sulfate.

(f)[1]

Name the process used when separating the aqueous copper(II) sulfate from excess copper(II) carbonate in step 2.

(g(i))[2]

Suggest what the term saturated solution means.

(g(ii))[1]

What observation would show that the solution was saturated in step 3?

(g(iii))[1]

Why should the aqueous copper(II) sulfate not be heated to dryness in step 3?

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: The amount is 0.0025 or 2.5 \times10⁻^{3} moles of H2SO4

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